1. Field of the Invention
The present invention relates to an orientation insensitive heat exchanger assembly for cooling an electronic device.
2. Description of the Prior Art
The operating speed of computers is constantly being improved to create faster computers. With this, comes increased heat generation and a need to effectively dissipate that heat. As laptop computers become more universal, the ability to position these heat exchangers and other parts in any one of numerous orientations become of greater importance.
Heat exchangers and heat sink assemblies have been used that apply natural or forced convection cooling methods to dissipate heat from electronic devices that are highly concentrated heat sources such as microprocessors and computer chips; however, air has a relatively low heat capacity. Thus, liquid-cooled units called LCUs employing a cold plate in conjunction with high heat capacity fluids have been used to remove heat from these types of heat sources. Although, LCUs are satisfactory for moderate heat flux, increasing computing speeds have required more effective heat sink assemblies.
Accordingly, thermosiphon cooling units (TCUs) have been used for cooling electronic devices having a high heat flux. A typical TCU absorbs heat generated by the electronic device by vaporizing a working fluid housed on the boiler plate of the unit. The boiling of refrigerant constitutes a phase change from liquid-to-vapor state as such the refrigerant of the TCU is considered to be a two phase fluid. Vapor generated during boiling of the refrigerant is then transferred to a condenser, where it is liquefied by the process of film condensation over the condensing surface of the TCU. The heat is rejected into a stream of air flowing over fins extending from the condenser and the condensed liquid is returned back to the boiler plate by gravity. As a result, most TCUs must be positioned in a predetermined orientation in order for the refrigerant to continue the boiling-condensing cycle, thus making the TCU orientation sensitive.
To solve this problem orientation insensitive thermosiphons, or heat exchangers, have been used. An example of a thermosiphon is U.S. Pat. No. 6,695,039 to Reyzin et al. Also relevant is U.S. Pat. No. 6,085,831 to DiGiacomo et al.
The '039 patent is a thermosiphon assembly including a housing for holding a refrigerant for liquid-to-vapor transformation, and heat transfer fins disposed in the housing. The housing includes one chamber which is in contact with a boiler plate for transferring heat from the electric device. The chamber extends upwardly at an angle such that the thermosiphon can operate in both a vertical and a horizontal position and any angle of tilt there between. However, the assembly cannot be rotated a full revolution while in a tilted or horizontal position and remain operational.
The '831 patent is a heat exchanger assembly including a housing for holding refrigerant and a top wall wherein heat transfer fins are disposed on the top wall. The housing includes a plurality of condensing chambers extending upwardly and outwardly along a single vertical plane. Although this assembly has a plurality of condensing chambers, refrigerant is not present in all chambers, nor are the chambers hermetically sealed.